The Ge-68 Line Source is used to calibrate PET systems. It is used as a transmission standard or source of annihilation photons to provide a tissue density correction for more accurate diagnostic scanning.

The source is mounted in a moveable holder which revolves around the patient’s head or body. The source emits photons which attenuate in the patient to varying degrees, depending on the location of the source with respect to the patient. The counter-opposed detectors on the PET system detect the radiation at any given point and the system software computes and stores this information. The instrumentation “corrects” the annihilation radiation intensity emitted from the administered radiopharmaceutical, automatically adjusting for the effect of the density and thickness of the tissue through which the photons travel at all the reference locations. This provides a “background corrected” scan of the patient to optimize resolution and to define more precisely the distribution of the radiopharmaceutical.